Abstract: At different water temperatures (14 ℃,19 ℃and 23 ℃), mensurating the number of Red blood cell (RBC) of Rainbow Trout and the activities of Alanine Aaminotransferase (ALT) and the ASpartese Tranasaminasa (AST) of serumof Rainbow Trout and the content of Total Protein (TP), Albumin (ALB), Globulin (GLO), Blood Sugar (BG), Total Cholesterol (TC), Triglyc eride (TG) and abio2microelement of serumof Rainbow Trout by using micro2arithmometer and HITACHI 7170A (automatic bio2 chemical analyzing apparatus) and BECKMAN CX23 (electrolyte analyzing apparatus) 1 The results showed that in trial water temperature range (14 -23 ℃), the number of RBC of Rainbow Trout reduced rapidly with water temperature rising, while the activities of Alanine Aaminotransferase of serum of Rainbow Trout increased with water temperature rising, but the activities of ASpartese Tranasaminasa increased during the water temperature in 14 -19 ℃ then declined during the water temperature in 19 -23 ℃; the content of Total Protein and Globulin of serum increased with water temperature rising, and the content of Albumin, Blood Sugar and Total Cholesterol increased during the water temperature in 14 -19 ℃then reduced during the water temperature in 19 -23 ℃, while the content of Triglyceride went down with water temperature rising ; the content of Cu of serumof Rainbow Trout decreased a little during the water temperature in 14 -19 ℃, but remarkably ascended during the water temperature in 19 -23 ℃ compared with Bighead Carp, but the content of K, P, Ca, Mg, Na and Cl of serum had unremarkable change1 This paper analyzed the change rule of the biochemical factor of Rainbow Trout at the condition of warm water, which could provide useful technical data for genic engineering of Rainbow Trout and Rainbow Trout breeding in warm water in south2 ward region, and could provide breaching way for playing down the response of Rainbow Trout to warm water1